Thought I'd post with some interesting updates.
It dawned on me the other day, that I could probably come up with a test, so to speak for my multipath issues I've been having. My theory was to unlock my modem from band 2 (let it connect to any band), and see if the other bands (I knew this would be band 12) see a similar difference in signal strength. I previously had tested these yagis, unlocked and they connected to band 12, but obviously the signal is much weaker than an antenna that is actually designed for band 12 (the yagis are band 2 specific). I suspected that, band 12, would not see as much of a difference, cause it just wouldn't be experiencing much multipath, or because the wavelength was much longer (coherence distance in multipathing is further with lower frequencies) Anyways, onto a screenshot:
As you can see, band 2 was selected as primary (not surprising given these antennas are tuned for band 2) and band 12 as secondary. If you look at the at the RSRP values, you'll see that band 12 values are much closer to each other between the two antennas, while band 2 (the PCC values) are still off by a large value.
Interestingly, this seems to be a really good combination, because I'm getting a little bit faster peak downloads while doing speed tests, and I still get really good uploads. Good uploads happen because the primary antenna and primary band is used for upload (no MIMO happens on upload) and because these antennas are such high gain, it means the cell tower gets a stronger signal from my modem, and subsequently higher modulation, and faster upload speeds (which is really what I want most, because my DSL upload speed is 1.25mbps!)
Lastly, the other morning I happened to notice that my modem had been kicked down to WCDMA (I think it could have been due to the poor weather, cause we had some heavy fog and rain that night). I was worried for a second, that the party was up, but I reset the modem and it immediately reconnected to LTE (band 2 & 12 again). I recalled that 'at!selrat' can be used to force LTE only, but in my experience this wasn't the case. Then I recalled that the 'at!band' command has a WCDMA+LTE band limit, or a LTE band limit only. I set it to LTE only in hopes that it won't randomly go back to WCDMA.